This invention relates to a pneumatic tire adapted to improve the driving comfort of a vehicle without causing a decrease in the driving performance of the vehicle including the maneuvering stability thereof.
It has strongly been demanded of late that a pneumatic tire has as its characteristics a capability of not only improving the driving performance of a vehicle including the stability thereof but also further improving the driving comfort of a vehicle. The driving comport dependent upon the quality of a tire is represented by an impact value of vibration and the magnitude of noise which are transmitted from a road surface to the interior of a vehicle via the tire. The path through which the vibration referred to above is transmitted to the interior of a vehicle passes a tread of a tire, outer and inner side walls thereof, outer and inner beads, a rim/disc and a vehicle body.
Therefore, in a conventional regularly-used method of improving the driving comfort of a vehicle, the rigidity of mainly both side walls of a tire is reduced by minimizing the dimensions of the bead fillers, whereby the force of restoring an external force which the side walls receive from the road surface is reduced.
However, when the rigidity of both side walls is thus reduced, the driving performance of a vehicle including the stability thereof decreases.
In accordance with the development of the front wheel driving techniques in the vehicle driving system utilized in recent years and the development of expansion of the space in the interior of a vehicle, the techniques for forming an asymmetric wheel structure in which the space in the inner part thereof is increased to as great an extent as possible has progressed, and a tendency to gradually increase the quantity of variation by which a position, in which a disc is connected to a rim, is offset from the center of width of the rim toward the outer surface of the wheel has been seen. The inventors of the present invention have made a study of the relation between an asymmetrically formed wheel and the propagation of vibration from a tire to the wheel to discover that there is close correlation therebetween.
The results of an investigation on the transmission rate of vibration propagated from the side walls of a tire to a wheel of an asymmetric structure show the following. A transmission rate of vibration propagated via a rim end at the outer side of a wheel is higher than that of vibration propagated via a rim end at the inner side of the wheel, and this tendency becomes more distinct in proportion to a distance by which a position, in which a disc is connected to a rim, is offset from the center of width of the rim.
The inventors of the present invention have thoroughly discussed such new knowledge with respect to the maneuvering stability of a vehicle to discover that, when this knowledge is skillfully utilized, the driving comfort of a vehicle can be improved with the maneuvering stability and driving comfort, which have a trade-off relation as mentioned above, kept compatible with each other.